2100 17 NOV 2012…. STAR DATE 201211.17
Most of the time when you are making the final Winter forecast …the months of October and November usually are not very active with respect to significant weather events. But as wel all know .. that has not been the case in 2012 with event of hurricane Sandy. This was followed shortly by the early November 7 nor’easter which bought significant snow to New Jersey New York City Connecticut and Long Island… and then now we have to deal with the ocean Low which is going to pass off the East Coast NOV 19-20.
This particular updated forecast will focus on several key aspects of the last 45 days in an attempt to figure out what the winter of 2012–13 is going be like. We’ll talk about
- snow cover over Siberia/ Eurasia during the month of October 2012
- Key upper air atmosphere weather patterns such as the arctic oscillation the North American oscillation and the western Pacific oscillation Sea surface temperature anomalies and what they may or may not imply
- And a few other odds and ends/ miscellaneous.
I suppose the first general question that has to be addressed is the concern that the events of late October and early November on the East Coast— specifically the historic event of hurricane sandy hitting the New Jersey Coast and the winter storm of November 7 — and whether those 2 events “mean” anything with respect to the upcoming winter. The basic answer is that the actual storms do not t mean anything one way or the other but the pattern which developed these particular events does have implications.
For example last year…on 28-29 October 2011 …there was a early season historic nor’easter which produced heavy snow over the interior portions of New Jersey southeastern New York and Connecticut into western and Central Massachusetts. It caused serious destruction of damage to the power infrastructure in CT. Since many of the forecasts– both with NWS/ CPC and many private sector – going into that winter of 2011-12 called for a another active cold and /or snowy winter in the eastern U.S…. the general perception or belief was that ….”if this is what the pattern is producing in late October of 2011 imagine what the winter is going to be like !!…”.
Yet as we all know the winter of 2011-12 was exceptionally mild and had very few significant winter storms anywhere the country but especially east the Rockies and East of the Mississippi River. On the other hand there have been Summer and Autumn patterns …such as the Hurricane season of 1995 which featured several significant East Coast hurricanes and noreasters in August Sept and Oct of 1995. Yet the pattern never shifted as we went into Winter of 1995-96 which produced several major East Coast snowstorms including the great January blizzard of 1996.
Over the past 20 years has been a lot of research done in various climate and meteorological periodicals which are shown in that autumn patterns do have a connection to the upcoming winter provided the autumn pattern is consistent and produces the same type of events. In other words the historic of 28 October 2011 inland snowstorm over the Northeast US was NOT part of a sustained Autumn pattern but a anomaly. Most of that autumn was warm and dry and the winter that followed was very much the same.
Keep in mind that the Spring and Summer of 2012 was exceptionally hot and dry over much of the country. It’s hard to remember that given what we seen in October and early NOV 2012. That dramatically shows how vastly different the overall pattern has turned.
THE UPPER AIR PATTERNS
Remember that the atmospheric PATTERNS are what drives the weather. It determines where LOWs will track… where the nice weather patterns are going to occur …where the cold air is going to move.. etc Weather models are supposed to reflect what’s going on in the atmosphere. They do not determine where weather systems actually move or develop. A Low pressure area over . Louisiana does not ”DECIDE” to move to Chicago or New York City because of a weather model. Weather features are not people and there is no decision-making process involved.
Far and away the two most important weather features or patterns which exist over the western hemisphere in determining the winter and the overall winter pattern has to do with the Arctic oscillation (AO) and the North Atlantic Oscillation (NAO). If you are not a weather not or hobbyist or meteorologist you may have heard of these terms used occasionally before but not know what these terms refer to. So let me briefly explain.
There are several distinct and noticeable weather patterns which developed in the upper levels of the atmosphere over the northern and southern hemisphere which tend to move in repeating cycles. These various Jet stream patterns in certain positions or certain “phases” produce weather patterns at the surface which will support a warm pattern …or a stormy pattern …or a cold pattern …or a wet pattern.. or some combination thereof. A good analogy might be to consider mountains or mountain ranges. We all know there are several different types of mountains and mountain ranges but no two of them or are exactly the same. But they all have the same general shape.
THE ARCTIC OSCILLATION .. or the AO
The Arctic Oscillation (AO) is one of the special and very important features which exists in the jet stream throughout the entire year. It has two distinct phases a POSITIVE phase and a NEGATIVE phase. These phases may vary in intensity ( weakly positive for example) but the important concept here to grasp is that when the AO is in one particular phase it strongly favors a certain type the weather pattern over North America and especially over Eastern North America including the U.S.. When the AO is in a different phase it has a equally strong impact on the weather patterns over Eastern North America but in a different way.
This image will show us how and why the Arctic Oscillation works and what it looks like. When there is a large area very cold air mass in the jet stream over the arctic regions — which shows up on the Jet stream map as having a big LOW over or North of the Arctic circle — the AO is said to be in the positive phase. The +AO keeps all the cold air bottled up over the arctic region and does not allow for large scale arctic outbreaks to occur either in Europe or in North America. This was exactly the case last winter which is why we had no significant colder outbreaks.
On the other hand when the AO is in the negative phase... which on the weather maps of the Jet Stream will come across as weak or small areas of Low pressure over the Arctic circle or sometimes a blocking pattern– it is much easier for large cold air masses to move out of the arctic regions into Europe and North America. This was exactly the case in the historic winters of 2009-10 and 2010-11.
This next image shows how this typically works. The two maps correspond to the different AO phases and it’s pretty self explanatory as these maps go. When you have a negative AO (the map on the left hand side) temperatures run Above Normal –relatively speaking of course — over the arctic region and especially over Eastern Canada and Greenland. And temperatures run below normal over the Midwest and the East Coast. When you have a negative AO (the map on the RIGHT hand side) shows exact opposite weather pattern . As you can clearly see the arctic regions are colder than normal and Central Russia is also much colder than normal …. while Eastern Canada central and eastern areas of the USA are much warmer than normal during the winter months.
However that being said simply having a negative or positive phase of the Arctic Oscillation doesn’t get us very far in figuring out weather patterns. It is quite possible that when the AO is Negative that the arctic cold air coming out of the arctic region goes into Europe but not into Canada or the U.S. So there of the things we have to take into consideration.
THE NAO– North Atlantic Oscillation
The North Atlantic Oscillation (NAO) is one of the special and very important features which exists in the jet stream throughout the entire year. It has two distinct phases –a POSITIVE phase and a NEGATIVE phase. These phases may vary in intensity ( weakly positive for example) but the important concept here to grasp is that when the NAO is in one particular phase it strongly favors a certain type the weather pattern over North America and especially over Eastern North America including the U.S.. When the NAO is in a different phase it has a equally strong impact on the weather patterns over Eastern North America but in a different way.
This image will explain our show how and why NAO is so important and the impact it has on weather patterns over North America in general and especially over the central and eastern U.S. during the cold season months. The diagram is pretty self explanatory but in a nutshell +NAO means a much reduced chance of saying any sort of significant colder outbreaks over the central and eastern U.S. and a much reduced chance of saying any sort of significant winter storm activity. When the NAO is in the Negative Phase… the odds significantly favor a colder than normal pattern with the potential for a significant cold air or arctic air outbreak… and the potential for some sort of significant East Coast or activity. Of course all of that is assuming that there is some sort of Low Pressure that is coming east. (In other words…. +NAO or – NAO do not produce winter storms or mild weather patterns by themselves.
The winter of 2011-12 featured a extremely positive NAO through almost the entire winter. In fact the OCT 2011 and NOV 2011 readings for the NAO were among the strongest ever seen. On the other hand OCT 2009 and OCT 2010 featured widespread persistently negative NAO which was also among the strongest ever seen. And we know that the winter is that followed.. 2009-10 and 2010-11 were quite snowy and cold).
These two particular Jet stream patterns … the AO and the NAO… give us several different possible combinations which forecasters MUST take into consideration in making the seasonal forecast …or even a forecast for the next 2 or 3 weeks. This image will show you the possible combinations that knowledgeable meteorologist and experience whether hobbyists are familiar with.
Let’s take a look at how the combination of the AO and the NAO often worked together and produce significant weather pattern or events for the eastern US.
This next chart shows us the NAO and the AO since August 1. I have highlighted some important features in order to ease the understanding of this significant chart.
The first thing that stands out is that for the most part the NAO and the AO have been synchronous or moving in this same general direction. This has not always been the case. Back during the snow-less or nearly snow-less winters of the 1980s and early 1990s… The charts back then show that the NAO and AO were not moving in the same direction and trends.
The first green box / rectangle shows the Heat wave breaking in early and mid August. Throughout most of APRIL MAY JUNE and JULY 2012 ….the NAO and AO were both strongly positive. However things began to change in early August which resulted when the NAO and the AO both turned sharply negative after AUG 4. Not surprisingly this is exactly when the heat wave broke and the first significant rains appeared over the Midwest.
The next green box is in early and mid September where again the NAO and AO both turned negative. And if you go back and take a look of surface weather maps you will see that in early and mid September we had our first significant blast of Autumn air over the central and eastern US .
However the third and largest green box that I have highlighted shows the prolonged and sustained negative NAO and negative AO which began in early October and reached a peak in the last week of October…. which is exactly when hurricane Sandy made its left turn and crashed into as southern NJ coast. There was a secondary drop in early November which is when Noreaster of NOV 7.
But this is not just the case for this particular autumn. If we go back and take a look of the last several winters we will also see that the severe and snowy winters of 2009-10 and the active snowy winters of 2010-11 featured sustained prolonged intervals of -AO and -NAO.
This image shows the AO and the NAO from the historic eastern U.S. winter winter of 2009-10. Notice that the Arctic Oscillation turned negative and strongly negative in October of 2009 then a briefly went towards positive in November and flipped two extremely negative during the heart of the winter. In fact the AO was the most negative EVER recorded during the heart of the winter months. The NAO was not nearly as strong but persistently negative during the heart of the winter months.
The result was a severe and historic winter for the East Coast.
This next image shows the following winter… 2010-11. Again notice that both the AO and the NAO in October of 2011 dropped moderately negative .. and the AO turned weekly positive during a good portion of November. But once we moved into the winter months both the AO and the NAO were consistently and strongly negative the the heart of the entire winter… up to early / Mid February of 2012.
Finally let us compare LAST WINTER… 2011-12 which as we all know featured very mild temperatures for all of the country east of the Rocky mountains to the East coast and very little snowfall. Throughout the entire Autumn of 2011 the AO and the NAO were strongly positive…. never once dropping into the negative phase. This of course is totally the opposite of what we saw in the previous two examples. Then once the winter of 2011-12 began … Both the AO and the NAO were consist only an strongly positive. As I stated above the AO was at or near record a positive levels.
WHAT ABOUT THIS WINTER ? WHAT WILL THE AO and NAO ” DO ” THIS WINTER?
As I stated and showed you above… having persistently strong -AO and -NAO in the month of October is a strong signal that the heart of the winter months will experienced large and n persistent prolonged periods of -AO and -NAO jet stream patterns. The October 2012 reading for the Arctic Oscillation was the second strongest on record– only exceeded by the October 2009 arctic oscillation reading! In fact if you look at all the top 10 negative arctic oscillation readings in the month of October… every one of those Winters that followed winter = DEC JAN FEB) featured persistently strong negative Arctic Oscillations.
OK… So the OCT AO strongly favor the AO running negative this upcoming winter. But what about the NAO? Over the past 10 years there has been some really great research done that shows a strong connection between SSTAs — sea surface temperature anomalies — in the North Atlantic during the month of October and forecasting the general trend of the NAO for the upcoming winter. This image clearly shows the connection between what the idealized or textbook example of the SSTA have looked like in the month of October and Winters which featured persistently negative NAO events.
The image is pretty self explanatory but basically there is a certain or specific type / pattern which we look for in the water temperatures over the north Atlantic.
There is often a pool of very warm ocean where temperatures– relative to normal of course– off the New England or Southeast Canada Coast– then a pool of cold water over the central north Atlantic east of Newfoundland — and a pool of warmer than normal sea surface temperatures in the Davis Straits ( the area between Labrador Canada and western Greenland).
This next image shows you what the current sea surface temperature in NOV 2012 look like over the north Atlantic. As of mid November we see a pool of very warm ocean where temperatures — relative to normal– off the New England Coast and Southeast Canada which matches the textbook or schematic of the classic SSTA for the negative NAO. We also see a very warm ocean where temperatures extending up into the Davis Straits. And we also see a pool of cold water in the central north Atlantic .
Interestingly if we compare the last three winters we see something important in different with regard to the SSTA and negative NAO. In this next image I am presented the last 3 Middle Novembers SSTA maps. — 17 NOV 2011.. 15 NOV 2010 and 16 NOV 2009 .
The first map clearly shows a very different looking SSTA configuration. Notice in the green circle that there is NO large body of warmer than Normal Sea surface temperature anomalies off the New England or Southeast Canada coasts. In fact the SSTAs temperatures there are colder than normal. This is the exact opposite of the textbook SSTAs diagram shown above that is needed for sustained negative NAO.
However the middle and right map of SSTAs from 15 NOV 2010 and 16 NOV 2009 .. show the exact opposite with classic or nearly textbook set up for sustained negative NAO patterns.
There has been a lot of research done over the past 10 years that shows a very strong connection between above normal snowfall over Siberia and the phase of the Arctic Oscillation. One of the lead researchers in this is Dr. Judah Cohen from AER. The correlation between the October snow cover over Siberia/ Eurasia and the AO is extremely strong … near 0.90. Basically the argument is … and in MY view it has been proven… that above normal snowfall in Siberia / Eurasia in the month of October strongly correlates to the negative phase of the AO. Likewise below normal snowfall over the same area in the month of October strongly correlates to the positive phase of the AO. Pretty simple really. You can read about how strong here… at this link. http://www.nsf.gov/news/special_reports/autumnwinter/model.jsp
But these images will also help show the correlation without getting too technical for some of you.
This next image shows the forecast for the temperatures across northern hemisphere in the winter of 2002-03.
For those of you that arw weather savvy… that winter was a historically significant winter with numerous significant winter storms over the Midwest and the East Coast and large areas of below normal temperatures on a persistent bases. The map of the LEFT side shows the temperature anomalies forecasted for that winter based upon the snow cover in October of 2003 which was much above normal. The map on the RIGHT hand side shows the actual temperature anomalies for the winter. That was a amazing forecast. But that was not a “lucky forecast”.
This next image shows the forecast made by Dr Cohen based upon the October 2009 snow cover in Eurasia of which was much above normal. This forecast cover the period from January February and March of 2010. The map of the LEFT hand side shows the forecast temperatures by Dr Cohen for JAN FEB MAR 2010. The map on the RIGHT hand side shows the actual temperature anomalies for JAN FEB MAR 2010. Again this was a exceptional forecast. As we know the Winter of 2009-10 was a historically significant winter with large areas of persistently below normal temperatures and above normal snowfall over the central and eastern US.
This method also works quite well over in Europe. The map of the LEFT was Dr. Cohen’s forecast for the temperatures of January February March 2010… again based primarily on the snow cover over Eurasia in October 2009. The map on the RIGHT shows actual temperatures in Europe for the same time frame. That is a stunningly good forecast.
And even more impressive was his forecast for the winter of 2011-12. While many others were calling for another colder than normal winter with significant snowstorm potential for the central and eastern U.S. Dr Cohen looked that the snow total for October 2011 and saw that it was substantially below normal over Eurasia.
This next image is the SNOW COVER from 22 OCT 2011 and we can see that the snowfall was in fact below normal over large portions of Canada and Eurasia
The map on the LEFT hand side shows his forecast for last winter 2011-12… And you can see that Dr Cohen went against the consensus and forecasted an exceptionally mild winter. The map on the RIGHT hand side shows the actual temperature anomalies from last winter. You should be impressed by this forecasting ability.
WHAT ABOUT OCT 2012 SNOW IN EURASIA?
This chart from FSU shows that during the last 45 days the snow cover has consistently run above normal over the northern hemisphere in general. But that does not tell specifically about Eurasia.
In this image here we can see this total SNOW COVER through November 14, 2012 and this snow appears to be much above normal . This matches the graph and from FSU.
The actual 31 OCTOBER 2012 snow total for Eurasia from the RUTGERS SNOW LAB …is 11.11 squared kilometers. The Rutgers snow Lab has data on snowfall coverage over the northern hemisphere… Eurasia Canada North America Greenland going back 45 years. The MEDIAN value of all these Octobers for SNOW COVER in Eurasia is 9.6 sq KM… the MEAN value is 9.88 sq KM.
Therefore the October 2012 SNOW COVER in Eurasia is much above normal by value of 1.21 square km above normal. This is the 11th snowiest October on record for Eurasia and closely matches the October 2009 value which was 11.28 sq KM. This next image gives us a summary of these facts and the last three winters.
In fact if we go back and time will continue see there is very strong correlation between the SNOW COVER over Eurasia in OCT. This next image shows a list of October Snow cover in Eurasia which preceded historically significant winters over the central and eastern U.S. As you can tell in almost every case where SNOW COVER was substantially above normal over Eurasia in October the following winter featured colder than normal temperatures and /or snowier than normal weather patterns.
Even more interesting is that if you go back and look at the early 1990s and most of the 1980s which featured very mild nearly snow less winters for much of the central and eastern U.S.. we see that on a consistent basis that in every case SNOW COVER was at or below normal in Eurasia during the month of October proceeding that winter. Now to be sure..some of these very low October SNOW COVER readings in Eurasia can be explained due to a extenuating circumstances. For example the October SNOW COVER in Eurasia of 1988 was during a very strong if not the strongest La Nina on record.
During the early 1990s… OCT 1990 OCT 1991 OCT 1992.. SNOW COVER in Eurasia during the October the proceeded those winters was substantially below normal and all three of those years also featured moderate to strong El Nino events. Indeed the period from 1983-84 to 1992-93 or perhaps that at least snowier this record in many of the big cities and the northeast U.S. And not surprisingly during this time frame …as I just showed.. SNOW COVER was substantially below normal in Eurasia in the month of October during that 10 year period.
Another way of looking at the impact of heavy SNOW COVER in Eurasia during the month of October preceding the winter is to look at this table from the Rutgers snow laboratory. This table shows the SNOW COVER for all the Octobers going back to 1967. And the correlation is really quite striking.
SUMMARY: the explosive development of SNOW COVER in Eurasia in October of 2012 is a very strong signal that not only will this winter be vastly different from the previous super mild winter … but is a strong indication that this winter will be close to what we saw on 2009-10. Combined with the very clear signal of a strong and persistent AO and NAO in OCT of 2012…. it is becoming increasingly hard to ignore all of these are strong indications.
OTHER WEATHER PATTERNS
Besides the arctic oscillation and the NAO there are several other important weather patterns in the jet stream which can influence the weather patterns over North America. One of them is the PNA– for the Pacific North America pattern.
This features is centered over the eastern Pacific and Western North America and is also strongly dependent upon large areas of Colder than normal or Warmer than Normal Sea surface temperature anomalies. This image explains how and why the PNA pattern works.
There are several different features in the atmosphere which can alter or cause the PNA to shift from positive to negative and backed off to positive again during the course of a winter Spring Summer or Autumn season. One of those features is the MJO… but another will feature which has to be taken into consideration are the SSTAs – sea surface temperature anomalies over the far eastern Pacific from Alaska down to Baja California
Over the past three years there has been a large and persistent pool of very cold ocean water temperature anomalies located in the eastern Pacific from Alaska down to Baja California. This large persistent pool of colder than normal ward temperatures as persistently favored ( which is called the cold Phase of negative of the PDO) has persistently favored a -PNA pattern.
We can see this persistent large pool of cold water here
During the winter months of 2009-10 and 2010-11– as I showed above — there was widespread high latitude blocking with strong persistent negative phases of the AO and NAO. As a result the -PNA did not cause a strong ridge to form over the eastern US and a winter stay persistently cold and stormy. However during the winter of 2011-12 the AO and NAO were persistently and strongly positive. As a result the -PNA pattern on the West Coast of North America did in fact produce a large and strong Ridge in the jet stream during the winter … and during the Spring and Summer of 2012. In fact this was one of the primary reasons WHY the Spring and Summer was so intensely hot and dry.
However if we look at the current mid November SSTA map we see that the ocean water temperature patterns over the eastern Pacific has changed considerably. There is no longer a massive pool of very cold sea surface temperatures in the eastern Pacific along the West Coast of North America.
THIS MEANS .. That the winter of 2012-13 could see +PNA patterns develop which would allow for serious and possibly severe arctic air masses to invade the central and eastern half of North America including the US.
THE WPO…. WESTERN PACIFIC OSCILLATION.
This Jetstream configuration is often overlooked by many but it sometimes can be significant especially if it is in a particular phase for prolonged period of time.
The POSITIVE phase of the WPO features a Upper Low in the jet stream over the Bering sea / far eastern Siberia and a ridge over the central north Pacific. This is exactly what we saw last winter. The NEGATIVE phase of the PDO produces just the opposite.. RIDGE over the Bering sea and far eastern Siberia and Low pressure over the central north Pacific. That is the current WPO phase as you can see here.. which is a pretty strong negative and persistent WPO event.
Assuming that the -WPO continues into December which seems a high probability…. The pattern strongly indicates that much of central and eastern portions of the U.S. as well as the Great Lakes and the Northeast will see temperatures run persistently Below Normal during the month of December and probably into January.
In the initial forecast assessment for the upcoming Winter of 2012-13 the which has issued back in the Middle October… I emphasize the point that the current an extremely strong negative phase of the QBO was a bit of a problem with regard to forecasting a cold winter. The research clearly shows that when the QBO is extremely negative ( with values of -20 or lower) going into the winter months… that the statistical correlation clearly favors a mild start to the winter which turns colder in the second half. That is assuming that the -QBO continues to weaken and move towards NEUTRAL in January February and March.
Since then the October reading for the QBO came out on November 3 and it showed some slight weakening but still a very strong negative QBO value -25. The latest data shows that as of mid November the QB oh has begun to weekend at a pretty steady pace and I suspect that on December 3 when the November values for the QBO are released by CPC we will see the QBO make a significant rise from say -25 to something like -14 or -13.
CFS MODEL FOR THE WINTER 2012-13.
Finally we can take a look at the climate model maps from the CFS. As a general rule there’s a lot of skepticism with regard to climate models and the ability to forecast anything correctly. That certainly has been the case with some of the more primitive models but the development and the arrival of the CFS version 2.0 has ended that skepticism. Back in the Spring season of 2012 the model anticipated El Nino conditions to develop and increase and as result … the CFS V2.0 forecasted a wet and cool Summer for the Midwest. However as we now know the El Nino conditions fell apart and the NAO and AO stayed strongly positive The CFS showed a dramatic shift in MAY of 2012 and correctly forecasted the severe outbreak of heat and dry conditions over all the Plains and the Midwest for June July and into early August of 2012.
Even more impressive is that in late July while anybody else was forecasting more extreme heat and dry conditions for August of 2012… the CFS in mid July I forecasted and significant change in the pattern with below normal temperatures and additional rainfall. Again the CFS was correct in showing this change and with the timing as well.
This first image shows us the December forecasts with respect to precipitation amounts. The map of the LEFT side is from the middle of October –specifically from OCT 14-23. As you can see it’s forecasting a fairly dry conditions over the Gulf coast and the Northeast and wet conditions over the Pacific Northwest and the entire West Coast. However the map on the RIGHT hand side shows the new forecast from earlier in November… NOV 3-12 to the specific. And it shows dramatically different weather patter which large areas of above and much above normal rainfall over the gulf coast into the Tennessee Valley and slightly above normal over the northeast and along the Pacific Northwest coast and the northern Rockies.
With respect to December 2012 temperatures the CFS model from 14-23 OCT showed a huge areas of much above normal temperatures covering all of the central lower Plains the Deep South into the Midwest and the Ohio Valley. The updated version however from early November shows a much different temperature forecast for DEC 2012. While it is true that in this second map that the Gulf coast and the East Coast are still quite warm … the warmth is not as intense and the CFS now shows a massive pool of very cold air covering all of western and Central Canada.
With respect to January precipitation... the CFS v2.0 in Middle October showed above normal rainfall or precipitation over the Gulf coast into the southeastern states while all other areas in the Conus was pretty much near normal. The November update showed a little more precipitation over the northeast… While Southern California the southwest states were much drier and the Pacific Northwest was wetter.
With respect to January temperatures the October forecast showed near normal temperatures for most of the Midwest and the northeast with slightly above normal temperatures over the gulf coast and the lower Plains… And a large area of below normal temperatures over southwestern Canada. The updated forecast from November from the CVS.. Showed a major expansion of that very cold air mass from southwest Canada into central and South Central Canada and all of Quebec. This is significant because it keeps all of the Midwest and the East Coast in near normal temperatures for January and close proximity of very cold air to the east coast could be significant with regard to snowfall and East Coast winter storms. The CFS also shows above normal temperatures over Texas and the southwest states into Nevada and Utah
With respect to February precipitation… The October version of the CFS showed very dry conditions over California and over the northeast with small areas of above normal rainfall over the Gulf coast and the Great Lakes. Once again however the updated version from early November of the CFS showed a major change. It has all of the deep south into the northeast and the lower Middle Atlantic states saying much above normal precipitation and the Pacific Northwest coastal areas turn drier.
With respect to February temperatures… Once again we see a huge shift in what the CFS models forecasting with regard to temperatures. The Mid OCT run showed a huge area of very warm temperatures covering all portions of the Plains the lower Midwest the entire Deep South and into the Middle Atlantic states. In addition it should be noted that the OCT CFS run showed no area of Canada in below normal temperatures. However the updated November run of the CFS showed a major changes with the new CFS now depicting a large pool of cold air over central and South Central Canada and over Quebec Canada. A very warm temperatures is now completely gone with only Southern Texas and the media gulf coast saying temperatures running slightly above normal while all of the Midwest and the East coast now seas near normal temperatures.
The historic East Coast hurricane sandy in late October and the noreaster on NOV 6-7 that followed are indicative of a significant change the pattern from the warm dry previous winter and the extreme Heat and drought the country experienced throughout the Spring and Summer 2012. Not only has the Arctic oscillation and North American oscillation shifted into persistent negative phase … but research shows that October seems to play a key role in determining the phases of the AO and NAO.
In addition significant changes in the sea surface temperature anomalies have occurred. In the eastern Pacific along the West Coast of North America the huge pool of cold water has dissipated and the new SSTAs configuration now supports +PNA development over Western North America. While we may not see this on a consistent basis I believe there will be some intervals during the heart of the winter into the spring where we will see several bouts of very amplified West Coast Ridging ( +PNA) in the jet stream. This could lead to strong arctic air outbreaks.
The early season development of much above normal snowfall in Eurasia during October is a strong indication that this winter will be much more like the winters of 2009-10 and 2010-11.
When all of these factors are taken into consideration there is no rational reason NOT to be bullish on the upcomcing Winter of 2012-13 over the eastern half of the continent and the U.S. in particular. The only restricting factor that I can see right now… is the very strong and negative QBO cycle which is only now beginning to weaken. The data from CPC that tracks the QBO on a daily basis does show significant weakening over the past two weeks. It is quite possible then that strongly negative QBO will rise to a value -10 or higher during the second half of the winter which would be extremely favorable for above normal snowfall and below normal temperatures over the eastern half of the country.